Means for preventing arcing between commutator-brushes.



PATBNTED APR. 26, 1904.

E. THOMSON. MEANS FOR PREVENTING ARGING BETWEEN GOMMUTATOR BRUSHES.

APPLICATION FILED MAY 29. 1903.

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N0. 758,157. PATENTED APR. 26,1904. E. THOMSON.

MEANS FOR PREVENTING ARCING BETWEEN OOMMUTATOR BRUSHES.

- APPLIIOATION FILED MAY 29. 1903.

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UNITED STATE Patented April 26, 1904.

PATENT OFFICE- ELIHU THOMSON, or sWAMrsooT'r, MASSACHUSETTS, ASSIGNOR TOGEN;

ERAL ELECTRIC COMPANY, A 'coaPoRATIo oF NEW Yorue MEANS FOR PREVENTINGARCING BETWEEN COMMUTATOR-BR USHES.

SPECIFICATION forming part of Letters Patent No. 758,157, dated April26, 1904. Application filed May 29, 1903. Serial No. 159,229. (Nomodel.)

ent potentials in the space through which the arcing would otherwisetake place. Preferably the material out of which the barrier or shieldis made is some non-combustible heatresisting non-disintegratinginsulating sub stance. Fused silicious matter, such as silicious sand orsilica or silica cemented by clay in the form of fire-resisting bricks,form suitable materials out of which the barrier may be made. In placeof these materials I may use compounds of asbestos with cementedmaterials. I prefer, however, to employ fused silica, which isnon-porous and stands excessive changes of temperature without crackingor disintegration.

For a better understanding of my invention reference may be had to theaccompanying drawings, in which I illustrate several embodiments of myinvention.

Of the drawings, Figure 1 is an end elevation, with parts broken away,showing one form of my invention. Fig. 2 is a partialsectional elevationof the same form. Figs. 3, 4, and 5 each show different arrangements ofthe barriers or shields; and Fig. 6 is a sectional elevation of abipolar motorhaving its brushes and barriers arranged as in Fig. 3.

In all of the figures of the drawings an armature-shaft A of adynamo-electric machine is shown upon which is mounted an armature B andcylindrical commutator C. The field of the machines comprises two ormore poles D. The armature and poles are not shown in all the figures ofthe drawings. Two brushes E E bear against the commutator.

railway-motor.

In Figs; 1 and 2. of the drawings'I have 5 conventionallyshown afour-pole .tWo-brush The brushes-E E are placed in position to engagethe commutator on its upper side and are separated from each other by anarc of ninety degrees, the armature beand between the brushes E E. Inthe construction which I have illustrated in the drawings the block-F isprovided with an integral extension G, by which the block may besecuredto a lug or projection H, which extends 5 from or is carried by themotor casing or frame in any suitable manner. This block F may be of alength somewhat less than the distance between the brushes E E and maybe separated from the commutator only far 7 enough to provide suitableclearance, and under some circumstances it may rest in contact with thecommutator.

When the blocks Fare in place, no'arcing or flashing over can occurunder ordinary circumstances. The block itself being quite massive andbeing formed out of non-conducting material and the space, if any, whichexists between the inner curved surface of the block and the outer edgesof the commutatorsegments being small, any are which may be formed orstart to formis cooled and smothcred and cannot maintain itself.

In Fig. 3 I have shown the brushes E bearing against the surface of thecommutator C' 5 at diametrically opposite points. The barriers orshields F in this case are shown as extending through an angle of nearlyone hundred and eighty degrees.

In Fig. 4 the brushes E are at diametrically 9 opposite points of thecommutator C, as in Fig. 3. Instead of employing a single shield orbarrier, however, a plurality of-barriers or shields are employed. Thebarriers or shields F above the line of commutation are held inclasp-like holders I, while the blocks F below the line of commutationare formed with grooves in their sides and are held inposition by wiresJ, which extend parallel to the axis of the shaft and engage with thewalls of said groove.

The use of a plurality of barriers or shields, as shown in Fig. 4, isdesirable in substations, as with such a plurality of barriers it iseasier to make adjustments which become necessary from time to time tocompensate for the wear of the commutator and of the barriers or shieldsif they be in contact with the commutator. IVhen the barriers or shieldsare in contact with the commutator, it will of course be understood thatsuitable lubrication may be made in order to avoid undue frictionbetween the parts.

In Fig. 5 I have illustrated a motor intended to rotate only in thedirection indicated by the arrow. The brushes are diametrically opposedwith respect to the commutator. The barriers or shields F in this case,however, extend throughout only a comparatively small portion of theentire are between the brushes and are placed each immediately inadvance of the brushes of the commutator, having reference to thedirection of rotation of the machine.

WVhen the machine is intended to rotate in one direction only, it shouldbe so designed that the magnetic field tends to drive the are or arcswhich may be formed between brushes in the direction indicated by thearrow in Fig. 6 away from the inner ends of the commutator-segments andthe armature and under the barrier F WVhile my invention is generallyapplicable in the operation of dynamo-electric machines, it isparticularlyuseful in connection with railway-motors, which by reason ofthe very sudden changes in the load put upon them and by reason of thesudden opening and closing of circuit produced by failure of the trolleyor contact shoe to continuously engage the supply-conductor areespecially liable to areing troubles.

What I claim as new, and. desire to secure by Letters Patent of theUnited States, is-

I. In combination, a commutator, brushes in operative relationtherewith, and a barrier or barriers of non-conducting material in thespace between the brushes.

2. In combination, a commutator, brushes therefor, and means forpreventing sparking between the brushes comprising a shield or barrierof fused silica located between said brushes.

3. In combination, a commutator havingits operative surface cylindrical,brushes engaging said cylindrical surface, and an arc-shaped shield orbarrier of non-conducting material located between adjacent brushes ofdifferent material.

4. In a dynamo-electric machine, a lieldproducing member, an armature, acommutator, brushes therefor, and a shield or barrier interposed betweenadjacentln'ushes of differ ent polarities, said field and said armaturebe ing so arranged that the field tends to force an are between thebrushes away from the armature and under the barrier.

5. In combination, a rotating commutator, brushes therefor, and meansfor preventing sparking between the brushes comprising a shield orbarrier of a fused silica placed slightly in advance of each brushhaving reference to the direction of rotation of the commutator.

In witness whereof I have hereunto set my hand this 27th day of May,1903.

ELIHU THOMSON.

WVitnesses:

DUcALn McK. MoKILLor, Jenn A. MoMANUs.

